1. Field of the Invention
This invention relates to the field of devices used to protect public drinking water during and after water main construction, specifically to a tri valve backflow prevention apparatus and a method of its use with a temporarily installed conventional backflow prevention assembly between existing water main pipe and a newly constructed, repaired, or upgraded section of water main pipe, to provide water needed at the construction site for pipe testing and other purposes. Its advantages relate to the temporary backflow prevention assembly being exclusively connected to it, and not to the water main pipe under construction, whereby when pressure and bacterial testing in the constructed pipe is successfully completed and the temporary assembly is removed after construction for use elsewhere, water is not drained from the constructed pipe, as in prior art methods of water main construction in common use today. Water draining into the construction hole not only compromises worker safety, it subjects the opened pipe to a risk of bacterial contamination, causes additional good drinking water to be used for flushing the constructed pipe to remove possible bacterial contamination and then to refill the constructed pipe prior to its use for delivery of drinking water to the public, and also causes a need for further pressure and bacterial testing. Thus, with present invention use, inspection and testing time of new/added sections of water main pipe are significantly reduced which translates into a reduced job cost, labor and material cost are also reduced as no sleeve installation is required between existing and new sections of water main pipe to replace the removed temporary backflow prevention assembly, and the time required to activate the constructed pipe for delivery of drinking water to the public is significantly reduced as one simply shuts off the two side valves of the present invention and removes the temporary backflow prevention assembly, leaving the new/repaired/upgraded pipe filled with good drinking water and ready for immediate water delivery as soon as one chooses to open the main valve body of the present invention using its easily accessible keyed valve stem. Since no breach ever occurs in or between the existing and constructed water main pipe after the present invention is installed and successful pressure and bacterial testing are initially accomplished, the new/repaired/upgraded water main pipe can immediately be used, whereas with currently known prior art methods, much additional labor and material expense is required to activate the constructed pipe, and a large amount of good drinking water is unnecessarily wasted for additional flushing and refilling of the constructed pipe after temporary backflow prevention assembly removal. Further, with present invention use, the two new sleeve joints created after temporary assembly removal in prior art construction are avoided, which otherwise increase the after construction failure risk of the water main pipe. Use of the present invention also eliminates the increased health risk posed to public drinking water as a result of opening the new/repaired/upgraded water main pipe midway during construction and after the constructed pipe has initially satisfied needed pressure and bacteria testing requirements. The present invention tri valve apparatus has a unitary structure that incorporates two side valve bodies and a main valve body together within a single housing. Only the two side valve bodies remain open during construction and provide the points of connection for both ends of a temporary backflow prevention assembly. The two side valves of the present invention are only shut and plugged after successful pressure and bacteria testing of the constructed pipe is achieved, with the main valve body of the present invention being thereafter opened via its easily accessible keyed valve stem to let good drinking water into the new/repaired/upgraded water main pipe for delivery to the public. Thus, the main valve of the present invention is directly connected between the existing and new/repaired/upgraded water main pipe at the outset of construction, and it remains in place even after the pipe construction is complete and the temporary assembly is removed from the side valve bodies, becoming a permanent part of the water main structure during its useful life and until it needs refurbishment or replacement.
2. Description of the Related Art
To protect public drinking water during the construction of new sections of water main pipe, and the upgrading of existing sections of water main pipe, a jumper system is commonly used. However, use of a jumper system has many disadvantages, including potentially adverse affects on worker safety and/or the safety of the drinking water to be delivered to the public via the new or repaired/upgraded sections of water main pipe. A jumper system involves the installation of one end of a temporary backflow prevention system using angled pipe fittings onto an existing water main valve and installation of the opposing end of the same temporary backflow prevention system to a section of new or repaired/upgraded water main pipe, also using angled pipe fittings. However, such an installation of a temporary backflow prevention system typically creates an approximate eight foot separation between the new/upgraded and existing sections of water main pipe that will ultimately need to be connected together after the temporary backflow prevention system is removed. However, before removal of the temporary backflow prevention system, installation of the new or upgraded section of water main pipe must be completed and it must successfully pass all pressure and bacterial testing requirements. The problems begin to occur when the temporary backflow prevention system is removed, as all of the water in the new or upgraded sections of water main pipe used for its testing is lost, and then the new or upgraded water main pipe needs to be refilled, re-flushed, and successfully pass additional pressure and bacterial contamination testing prior to being used for drinking water delivery. One important problem associated with the removal of the conventional temporary backflow prevention system just described is that the contractors performing the new main construction typically excavate back down to the whole area of the existing water main valve and the new or repaired/upgraded water main pipe, and then when the jumper system is removed, all of the water in the new or repaired/upgraded water main pipe that was used for its testing drains into the working hole. This causes the waste of hundreds of gallons of good clean drinking water, and further leaves the existing valve and new or upgraded water main pipe open and exposed to the possible entry of bacteria, a procedure that defeats the pre-testing step of chlorinating the inside of the new or repaired/upgraded sections of water main pipe to make them bacteria-free. Worker safety can also be compromised by the water drained into the excavation hole. Further disadvantages of the commonly used jumper system involve the tie in of the new or upgraded water main pipe, which is completed by use of a retrained ductile iron sleeve to connect the new or repaired/upgraded water main pipe to the existing water main shut-off valve, followed by flushing of the new/upgraded/repaired water main pipe with water to remove all of the air therein. The tie in takes extra inspection hours, extra man hours, extra equipment hours, extra material cost, wasted large amounts of good water, and even then there is no guarantee that the new water line is free of bacteria.
In contrast, the tri valve of the present invention is not removed and eliminates all of the above-mentioned problems. The main valve of the tri valve present invention is only opened after its two side valves used during construction are closed and plugged. Also, during use of the present invention tri valve, the existing water main pipe is sealed off at all times from bacteria intrusion. Further, the added cost of providing the present invention tri valve is minimal when compared to the total cost of prior art water main installations and/or upgrade that include extra man hours and equipment time needed for additional pipe flushing and inspection, the amount of good potable water wasted during jumper removal and the additional pipe flushing needed to remove air and possible bacterial contamination, and the safety risk posed to the drinking water provided for the public. No other apparatus or method is known that functions in the same manner or provides all of the advantages of the present invention.